Storage capacity of H₂ in a kind of potassium-modified multiwalled carbon nanotubes, K⁰-MWCNTs, was measured by using high-pressure volumetric method combined with desorption water- displacement method. It was experimentally shown that appropriate incorporation of a certain amount of metallic potassium into the MWCNTs could significantly increase the storage capacity of hydrogen. Under conditions of 7.25 MPa and ambient temperature, H₂ uptake of 3.8 wt% could be achieved by the x%K⁰-MWCNTs (x%＝30%～35%, mass percentage), which was 2.5 times as high as that by the K⁰-free MWCNTs under the same conditions. It was also indicated that adsorption of 99% of the H₂ was reversible, and that 88% of the stored hydrogen (equalling storage capacities of 3.36 wt%) could be desorbed while the pressure was relieved to atmospheric pressure and ～11% of the stored hydrogen (equalling storage capacities of 0.41 wt%) was desorbed in the following process of elevating temperature from room temperature to 673 K. The Raman-spectroscopic and TPD-MS/GC investigations of the H₂/K⁰-MWCNTs adsorption systems showed that adsorption of H₂ on the MWCNTs could occur in associative and dissociative forms, with the observed ν_s(C—H) for CH₂, ν(C—H) for CH and ν(H—H) for H₂ (a) at 2856, 3228 and 3946 cm^－1, respectively, and that H₂ was the predominant products desorbed at temperatures lower than 723 K, whereas in addition to H₂, light hydrocarbons such as CH₄, C₂H₄, C₂H₂, etc. were also involved in the products desorbed at temperatures higher than 723 K.

Key words: MWCNTs, K⁰-MWCNTs, hydrogen-storage, Raman spectra of H₂/K⁰-MWCNTs